Polycarbonate resins are representative thermoplastic materials having a thermal deformation temperature of about 135° C. or more. Polycarbonate resins can exhibit excellent mechanical properties, such as impact resistance, and excellent self extinguishability, dimensional stability, heat resistance and transparency. Polycarbonate resins thus have been widely used in the manufacture of exterior materials for electric and/or electronic products, office equipment, and automobile components, and as optical materials for optical disc substrates, various lenses, prisms, optical fibers, and the like.
However, polycarbonate resins exhibit low scratch resistance, which limits the use of polycarbonate resins as exterior materials. In order to supplement scratch resistance of polycarbonate resins, a separate scratch resistant film may be applied to a polycarbonate film. However, the scratch resistant film can be expensive and manufacturing costs can be increased due to an additional coating process.
Thus, research has been devoted to improving scratch resistance of polycarbonate resins. A widely used method for improving scratch resistance of polycarbonate resins is blending a polycarbonate resin with a resin having scratch resistance.
Although such a blending method can slightly improve scratch resistance, this method can provide an insignificant effect, and thus a fundamental measure for improving scratch resistance of polycarbonate resins is demanded.
Specifically, when a polycarbonate resin is blended with an acrylic resin to improve scratch resistance, there can be drastic deterioration in impact resistance. Also there can be significant increase in haze due to poor compatibility between the resins to be blended, which can significantly deteriorate transparency of the polycarbonate resin. Further, acrylic resins can be easily broken. Thus, when an acrylic resin is blended with a polycarbonate resin, films prepared from the blended resins can have low elongation, and are not suited to a roll form. Typically, films for industrial use must be prepared in roll form for the purpose of loading, transportation, and the like. However, such low elongation of the films results in undesirable moldability, thereby restricting the use of the films in industrial applications.
In addition, when plastic materials are used for films, the films are often painted for the purpose of decoration. In this case, paints may be diluted with various organic solvents, applied to a surface of the film, and then dried. During this process, the organic solvents used as diluents can penetrate into polycarbonate, causing deterioration in transparency and mechanical strength of the film. Thus, in order to form a polycarbonate resin film by painting and the like, there is a need for improvement in chemical resistance of a polycarbonate resin.
Korean Patent Publication Nos. 2007-0071446A, 2009-0026359A and 2010-0022376A disclose a method for improving chemical resistance of a polycarbonate resin by blending the polycarbonate resin with other resins having chemical resistance. Although such a method may slightly improve chemical resistance, this method provides an insignificant effect and can cause deterioration in impact resistance. Further, in order to enhance impact resistance deteriorated by blending, an impact reinforcing agent may be employed. In this case, however, significant decrease in transparency of the resin can be encountered.
Japanese Patent Publication No. H5-339390A and U.S. Pat. No. 5,401,826 disclose a method for improving chemical resistance by manufacturing a copolymerized polycarbonate in which a material having chemical resistance is incorporated into an existing polycarbonate resin. As one example of the chemically resistant material to be copolymerized, 4,4′-biphenol is copolymerized in the preparation of polycarbonate resins, thereby improving chemical resistance. However, although the polycarbonate resin may have improved chemical resistance by the use of 4,4′-biphenol, impact resistance of the resin may be lowered, thereby deteriorating the merits of the polycarbonate resin. As the amount of 4,4′-biphenol increases, flowability of the resin is drastically decreased, thereby deteriorating moldability.
Therefore, in order for polycarbonate resins to be used in the preparation of films, there is a need for a polycarbonate resin having excellent scratch resistance, elongation and chemical resistance without deterioration in inherent physical properties of the polycarbonate resin, such as impact resistance, transparency, and the like.